Many food manufacturers have reduced the sodium content of their products since 2005, but some have added more salt than ever according to a report published by the Center for Science in the Public Interest (CSPI). The researchers compared the sodium content of 480 packaged and prepared foods in 2011 with levels recorded for the same foods in 2005, finding mixed results overall and wide variation within food categories such as breads, cheeses, salad dressings, soups, pizza, and French fries. With over 70 million Americans suffering from high blood pressure, the report calls on food manufacturers to accelerate sodium reductions and urges the FDA to set gradual sodium limits.

Analyses of the overall data in "Salt Assault" were published last month in a paper in JAMA Internal Medicine co-authored by Northwestern University Feinberg School of Medicine Steve Havas and Robert J. McCarter of the Children's National Medical Center, but the new report provides detailed information about each of the foods surveyed.

Of the 480 products tracked over that six-year period, sodium decreased in 205 (42.7 percent), increased in 158 (32.9 percent), and did not change in 117 (24.4 percent). Sodium increased in 34 products by 30 percent or more, while only 26 products decreased by the same magnitude. For instance, Ragu Old World Style Traditional Spaghetti Sauce had almost 40 percent less sodium in 2011 than 2005. Meanwhile, Hardee's raised the sodium in its medium French fries more than any other product monitored, having three times as much salt in 2011 compared to 2005. Even some organic brands had higher sodium levels, such as Whole Foods’ 365 Organic Tomato Sauce with a 93 percent increase, and Organic Valley Organic Low Moisture Mozzarella, with an 81 percent increase since 2005.

"Clearly, there's a major opportunity for many food manufacturers to bring sodium down to the lower levels used by some of their competitors," said CSPI executive director Michael F. Jacobson.

While CSPI's survey found little overall change in the 480 foods, in the past several years most of the largest companies have begun lowering sodium levels, with some of the changes made after 2011, the year of CSPI's survey. The nonprofit group has partnered with the Grocery Manufacturers Association and the National Restaurant Association to sponsor conferences encouraging their members to lower the sodium content of their offerings. Continued discussion with industry is taking place this week at the American Heart Association's "Strategies to Reduce Sodium Intake" conference in Arlington, Virginia.

McDonald's and Kraft, for instance, say they have lowered sodium by an average of about 10 percent. General Mills and ConAgra both plan to lower sodium by 20 percent by 2015. And Wal-Mart, the nation’s biggest grocery chain, is aiming for a 25 percent average reduction in the sodium content of its house brands by 2015 and has asked all of its suppliers to do the same.

CSPI estimated that companies would have to reduce sodium by half in order for healthy, young, white adults to reach the recommended 2,300 mg per day level and by 70 percent for others to achieve the 1,500 mg level recommended for them. "We are skeptical that reductions of this magnitude could be achieved without government interventions, such as those suggested by the Institute of Medicine's 2010 report," explained Jacobson. He added that consumers shouldn't wait until industry improves packaged foods. Americans should read labels carefully, but also should eat more fruits, vegetables, and other unprocessed foods that contain relatively little sodium.

The 2010 IOM report recommended that the FDA and USDA set sodium limits for categories of processed foods that are the biggest sources of sodium. The limits could be based on the current lowest levels in each category, and companies could be given several years to comply.